Does the resolution never appear it map files ?
Resolution is no stored in the density files.
What is the incidence/relevance of "arbitrarily" setting this parameter such as it is apparently done in this example ?
Setting a wrong resolution will lead to wrong fitting results. In the next steps of the procedure we simulate the template protein to the resolution of the map and apply a cross-correlation measure to compare between the two. If the smoothed template significantly differs from the density map we will not be able to get correct solutions.
If I get it right; though this parameter is critical for computations, the resolution is not stored in density files. HENCE you have to remember the resolution of your map, so that you can fill this parameter in the map header when you load it in IMP.
In fact, I think I don't really understand the notion of resolution in Cryo EM, or maybe it is just in IMP. I have an intuition from my experience with RX structures, where resolution has something to do with the precision and size of data used for the density map generation; and ultimately represents some kind of a "level of detail".
In order to better understand the two notions, I used IMP.em.SampledDensityMap and IMP.em.write_map to generate density maps of a structures with different values for voxel size and resolution. It appears that increasing the resolution of a map (while keeping the size of a voxel unchanged) indeed blurs the information and "potatoes" isodensities, which is fine; but for some reason it also affect the data size : the bigger the resolution, the bigger the map size (in angstrom as well as in number of voxels). Is this normal a behavior ?